Method for printhead cleaning using mobile maintenance carts

ABSTRACT

A maintenance method for a three-dimensional printer includes operating a platform to move along a second track past a first position where the second track is coupled to a first track, and along the first track in a process direction to a position opposite an ejector head positioned opposite the first track. The method operates the platform to (1) perform an operation on the ejector head positioned opposite the first track, (2) move the platform along the first track to a second position that is past the ejector head in the process direction, and (3) operates a switch to selectively couple the first track to the second track at the second position. The method also operates the platform to move past the second position to enable the platform to return to the second track.

PRIORITY CLAIM

This application is a divisional application from and claims priority toU.S. patent application Ser. No. 14/692,847, which is entitled “SystemArchitecture For Printhead Cleaning Using Mobile Maintenance Carts,”which was filed on Apr. 22, 2015, and which issued as U.S. Patent Numberx,xxx,xxx on mm/dd/yyyy.

TECHNICAL FIELD

This disclosure relates generally to printing systems, and inparticular, to maintenance devices used in three-dimensional objectprinting systems.

BACKGROUND

Digital three-dimensional manufacturing, also known as digital additivemanufacturing, is a process of making a three-dimensional solid objectof virtually any shape from a digital model. Three-dimensional printingis an additive process in which one or more printheads eject successivelayers of material on a substrate in different shapes. Typically,ejector heads, which are similar to printheads in document printers,include an array of ejectors that are coupled to a supply of material.Ejectors within a single ejector head can be coupled to differentsources of material or each ejector head can be coupled to differentsources of material to enable all of the ejectors in an ejector head toeject drops of the same material.

Materials that become part of the object being produced are called buildmaterials, while materials that are used to provide structural supportfor object formation, but are later removed from the object are known assupport materials. Three-dimensional printing is distinguishable fromtraditional object-forming techniques, which mostly rely on the removalof material from a work piece by a subtractive process, such as cuttingor drilling.

A previously known three-dimensional object printing system 10 is shownin FIG. 11. In the view depicted in that figure, a platform 14, called acart, includes surfaces 18 (FIG. 10) that slide upon track rails 22 toenable the cart to move in a process direction P between printingstations, such as the printing station 26 shown in FIG. 11.Alternatively, carts can include wheels configured to roll along tracks,or other types of acceptable mobility mechanisms. The rails 22 terminateat a position underneath the cart 14 as shown in FIG. 11. Printingstation 26 includes four ejector heads 30 as shown in the figure,although fewer or more ejector heads can be used in a printing station.Once the cart 14 reaches the printing station 26, the cart 14transitions to precision rails 38, which begin at the termination of therails 22, to enable bearings 34 to roll upon precision rails 38.Precision rails 38 are cylindrical rail sections that are manufacturedwithin tight tolerances to help ensure accurate placement andmaneuvering of the cart 14 beneath the ejector heads 30. The rails 38terminate past the printing station 26, as shown in FIG. 8, whereanother set of rails 22 (not shown) begin and then lead to the nextprinting station. Linear electrical motors are provided within housing42 to interact with a magnet positioned with housing 46 connected to thelower surface of the cart 14, as described below, to propel the cart asthe surfaces 18 slide along the track rails 22 and then, once thebearings 34 transition to the precision rails 38, maneuver the cart 14on the precision rails. As the cart 14 moves on the rails 38 past theprinting station 26, the printheads eject material onto the uppersurface of the cart in synchronization with the motion of the cart.Additional motors (not shown) move the printing station 26 verticallywith respect to the cart 14 and in an X-Y plane parallel to the uppersurface of the cart as layers of material accumulate to form an object.Alternatively, a mechanism can be provided to move an upper surface ofthe cart 14 on which the object is being formed vertically and in theX-Y plane to enable the layers to form the object. Once the printing tobe performed by a printing station is finished, the cart 14 is moved toanother printing station for further part formation, layer curing orother processing.

An end view of the system 10 is shown in FIG. 10. That view depicts inmore detail the surfaces 18 on which the cart 14 slides the track rails22. Bearings 34 of the cart 14 are positioned on the precision rails 38in an arrangement that facilitates accurate positioning of the buildplaten on the cart 14. Specifically, bearings 34 are positioned at aright angle to one another on one of the rails 38 to remove 4 degrees offreedom of the cart 14, while the other bearing 34 rests on the otherrail 38 to remove one more degree of freedom. Linear motors within thehousing 42 generate electromagnetic fields that interact with the magnetin housing 46 to move the cart 14 over an upper surface 50 of thehousing 42. Gravity and magnetic attraction between the linear motorsand the magnet hold the bearings 34 in contact with the rails 38.

Material ejected by the ejector heads 30 as well as other contaminantscan accumulate and present a risk of damaging or impacting the accuracyof the ejector heads 30. For example, material within an ejector headcan solidify to form a clog or partially obstruct the ejector head.Material from other ejector heads or other particulates can contaminatethe ejector head. Similar risks are also present for other printingstations in the printing system 10.

Material that has accumulated on an ejector head or other printingstation, or extraneous material from an improperly maintained ejectorhead can present other risks. When carts are not present underneath theejector heads 30, errant drips of materials can fall from the ejectorheads and produce undesired debris and contamination on the precisionrails 38 and the housing 42. Also, air-borne contaminants in theenvironment, such as dust or other particulate matter, can fall andcollect on the rails 38 and the housing 42. When these contaminants anddebris are located at any interface between the bearings 34 and therails 38, the linear velocity of the cart is disrupted and the qualityof the printed object is affected. Similarly, when these materials arewithin the gap between the top surface 50 of the housing 42 and themagnet 46, the magnetic attraction can be affected and enable the cartto be less constrained. Additionally, the collection of material dropson top of the housing 42 can also affect the dissipation of heat fromthe motor and cause motion quality disturbances, impacting theperformance and reliability of the motor. In order to producethree-dimensional objects with acceptable quality, the motion of thecart 14 beneath the ejector heads 30 needs to be precise. Therefore,improvements in three-dimensional printing systems that help prevent thecontamination on the precision rails and motor housing that affects theaccuracy of the placement and movement of the cart would be beneficial.

Regular maintenance to the ejector heads 30 and other printing stationsis beneficial for maintaining accurate and efficient operation of theprinting system 10, and for preventing material and other contaminantsfrom accumulating on the precision rails and motor housing. Conventionalthree-dimensional printing system maintenance devices often requirelengthy interruptions of the printing process, and include complexmachinery beyond the components necessary for three-dimensional printingthat can increase the machine footprint of the system. One example of aconventional maintenance device includes a maintenance cabinet separatefrom the printing system 10 that can be positioned next to a printingstation to be maintained. The cabinet contains tools usable to maintainthe printing station. In another example, an ejector head is moved toengage with a maintenance station configured to maintain the ejectorhead. Including a maintenance architecture that does not interrupt theprinting process and that does not significantly increase the footprintof the printing system would be beneficial.

SUMMARY

A maintenance system for a three-dimensional printer that incorporatesmobile platforms includes a first track, and a platform that is operableto move along the first track in a process direction. An ejector head ispositioned opposite a first portion of the first track. The maintenancesystem further includes a second track that is coupled to the firsttrack at a position prior to the platform reaching the ejector head, andthat is configured to selectively couple to the first track at aposition that is after the platform passes the ejector head in theprocess direction. A disposal unit is positioned opposite a secondportion of the second track. The maintenance system further includes acontrol that is configured to operate the platform to move along thesecond track to the position where the second track and the first trackare coupled to enable the platform to move along the first track in theprocess direction past the ejector head, operate the platform to performan operation on the ejector head, operate the platform to move to theposition where the first track selectively couples to the second trackafter the platform passes the ejector head in the process direction toenable the platform to return to and move along the second track, andoperate the disposal unit to remove three-dimensional print media fromthe platform.

A three-dimensional object printing system with an incorporatedmaintenance system includes a first track, and a platform that isoperable to move along the first track in a process direction. Anejector head is positioned opposite a first portion of the first track.The maintenance system further includes a second track that is coupledto the first track at a position prior to the platform reaching theejector head, and that is configured to selectively couple to the firsttrack at a position that is after the platform passes the ejector headin the process direction. The maintenance system further includes acontrol that is configured to operate the platform to move along thesecond track to the position where the second track and the first trackare coupled to enable the platform to move along the first track in theprocess direction past the ejector head, operate the platform to performan operation on the ejector head, and operate the platform to move tothe position where the first track selectively couples to the secondtrack after the platform passes the ejector head in the processdirection to enable the platform to return to and move along the secondtrack.

A method for maintaining a three-dimensional object printing systemincludes operating a platform to move along a second track past a firstposition where the second track is coupled to a first track, and alongthe first track in a process direction, operating the platform toperform an operation on an ejector head positioned opposite the firsttrack, operating the platform to move along the first track to a secondposition that is past the ejector head in the process direction,operating a switch to selectively couple the first track to the secondtrack at the second position, and operating the platform to move pastthe second position to enable the platform to return to the secondtrack.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the present disclosure areexplained in the following description, taken in connection with theaccompanying drawings.

FIG. 1 is a perspective view of an exemplary three-dimensional objectprinting system having a maintenance system that is integrated with theprinting process performed by the object printing system.

FIG. 2 is a schematic view of an exemplary embodiment of athree-dimensional object printing system having a maintenance systemthat is integrated with the printing process performed by the objectprinting system.

FIG. 3 is a perspective view of an exemplary embodiment of a platformusable in a three-dimensional object printing system.

FIGS. 4 and 5 are different exemplary embodiments of receptacles forremoving material from a platform of a three-dimensional object printingsystem.

FIGS. 6 and 7 are perspective views of different exemplary embodimentsof printhead maintenance devices attached to a platform usable in athree-dimensional object printing system.

FIG. 8 is a perspective view of another exemplary embodiment of aplatform usable in a three-dimensional object printing system.

FIG. 9 is a schematic view of another exemplary embodiment of athree-dimensional object printing system that incorporates hybridmedia-maintenance platforms.

FIG. 10 is a rear view of a prior art mobile cart enabled to move alonga rail track of a three-dimensional object printing system.

FIG. 11 is a perspective view of a prior art three-dimensional objectprinting system that includes a rail track and a mobile cart.

DETAILED DESCRIPTION

For a general understanding of the present embodiments, reference ismade to the drawings. In the drawings, like reference numerals have beenused throughout to designate like elements.

FIG. 1 illustrates an exemplary embodiment of a three-dimensionalprinter 100 that incorporates at least one mobile cart 102. The printer100 includes a first track 104, a second track 106, and at least oneprinting station 108 positioned opposite a first portion 110 of thetrack 104. The mobile cart 102 includes a platform 112 that has amovement device 114, such as wheels or sliding surfaces, and isconfigured to move along the track 104. The platform 112 is configuredto support material for forming a three-dimensional object.

In general operation, the mobile cart 102 is operated to move along thefirst track 104 past the printing station 108, which includes at leastone ejector head configured to eject material onto the platform 112 ofthe mobile cart 102 to form a three-dimensional object. The second track106 is configured to support at least one maintenance cart (not shown),described in further detail below. During a maintenance operation,maintenance carts can be operated to move from the second track 106 tothe first track 104 and pass by the ejector head to perform amaintenance operation on the ejector head.

Ejector heads for three-dimensional printing systems typically requiremaintenance over extended use, such as at regular intervals, after apredetermined number of printing operations, or upon detection of amaintenance issue, in order to maintain accuracy, efficiency, andoperability necessary for three-dimensional printing. Ejector heads canbecome obstructed or clogged with extraneous material, foreign materialscan contaminate or damage ejector heads, and material can build up onthe track 104 or other portions of the printing system 100 and interferewith the printing operation.

FIG. 2 illustrates a schematic view of a three-dimensional printingsystem 200 that incorporates a maintenance system that coordinates wellwith the printing process performed by the printing system 200. Thesystem 200 includes at least one platform, such as the platforms 202a-e, a first track 204, an ejector head 206, a second track 208, aswitch 210, a receptacle 212, and a controller 214. Pluralities ofactuators 215, 217 are positioned within a housing of the first andsecond tracks 204, 208 respectively. Each of the platforms 202 a-eincludes a plurality of wheels (not shown, see, e.g., FIG. 3) or othertypes of acceptable movement mechanisms, such as the sliding surfaces 18illustrated in FIG. 10, that are configured to engage with and rollalong the first and second tracks 204, 208 to enable the platforms 202a-e to move through the system 200.

Actuators 215 within the first track 204 are configured to operativelyengage with magnets positioned in or below the platforms to enable, forexample, the media platforms 202 a and 202 b to move along the firsttrack 204 in a process direction 216. While several actuators 215 areillustrated in FIG. 2, the reader should understand that actuators 215are distributed along the first track 204 in order to engage withplatforms 202 a-e as they move therealong, and that only several suchactuators 215 are illustrated in FIG. 2 for the purpose of clarity.Other types of actuators, such as motors powering the plurality ofwheels of a platform, conveyers, or blowers are also contemplated. Thereader should understand that in the present embodiment, the first track204 is a continuous loop, and the process direction 216 refers to adirection of motion around the loop which, in FIG. 2, iscounter-clockwise.

In one embodiment, the first track 204 include, in sections, cylindricalrails such as the precision rails 38 illustrated in FIG. 11, andincludes, in sections, slide rails such as the track rails 22illustrated in FIG. 11. In an embodiment, the first track 204 includescylindrical rails in sections opposite which printing stations arepositioned, and includes slide rails in sections without cylindricalrails. In one embodiment, the slide rails and cylindrical rails overlapeach other in the process direction, at least in part, to enableplatforms to transition therebetween.

The ejector head 206 is configured to eject material for forming athree-dimensional object, and is positioned opposite a first portion 218of the first track 204. As illustrated in FIG. 2, the first portion 218includes multiple printing stations in addition to the ejector head 206,such as a planarizing station 220, a UV cure station 222, and an imageanalysis station 224, but other configurations and numbers of printingstations are also contemplated. In one embodiment, at least one printingstation is located opposite another portion of the first track 204spaced apart from the first portion 218. Although illustrated as asingle ejector head, it should be understood that the ejector head 206can be an array of ejector heads. Moreover, the system 100 can includeadditional ejector heads or arrays of ejector heads positioned oppositethe first track 204.

The controller 214 is operatively connected to the actuators 215 of thefirst track 204 and to the ejector head 206, and is configured tooperate the actuators 215 to move media platforms, such as the platform202 b, along the first track 204 in the process direction 216. When amedia platform is opposite the ejector head 206, the controller isfurther configured to operate the ejector head 206 to eject materialonto the platform with reference to three-dimensional object data inorder to form a three-dimensional object. In some embodiments, thecontroller 214 is further operatively connected to a height actuator(not shown) configured to modify a distance between the platforms 202a-e and the ejector head 206 to enable three-dimensional printing atdifferent heights, layers, or distances. The height actuator can beincluded, for example, with the platforms 202 a-e, with the first track204 at a position opposite the ejector head 206, or with the ejectorhead 206. The controller 214 is also operatively connected to otherprinting stations and is configured to perform other printing operationsvia the other printing stations. The connections between the controllerand the other printing stations 220-224 are not shown in FIG. 2 for thepurpose of clarity.

The system 200 includes at least one maintenance platform, such as theplatforms 202 c-e. Maintenance platforms are operable to perform amaintenance operation on a printing station, such as the ejector head206. A second portion 226 of the second track 208 is configured tosupport maintenance platforms to enable a maintenance platform, such asthe platform 202 d, to remain on the second portion 226 during a timeperiod in which the platform 202 d is unused.

The second track 208 is coupled to the first track 204 at a firstposition 228 to enable maintenance platforms to move from the secondtrack 208 to the first track 204. The first position 228, on the firsttrack 204, is before the first portion 218 in the process direction 216such that a maintenance platform moving from the second track 208 to thefirst track 204 passes by the first portion 218 when continuing to movealong the first track 204.

The controller 214 is further operatively connected to actuators 217 ofthe second track 208. While FIG. 2 illustrates several of the actuators217, the reader should understand that additional actuators 217 can bedistributed along the second track 208. The actuators 217 are configuredto move maintenance platforms along the second track 208 towards thefirst position 228, onto the first track 204, and along the first track204 in the process direction 216. When a maintenance platform passes bya printing station, such as the platform 202 c passing by the ejectorhead 206, the controller 214 is further configured to operate themaintenance platform to perform an operation on the printing station,e.g., the ejector head 206. A particular platform can be operable toperform an operation on a particular printing station. In anotherexample, a platform can be operable to perform one or more operations onone or more different printing stations. For instance, the printingsystem 200 can include different maintenance platforms that are eachoperable to perform a different maintenance operation.

The first track 204 is selectively coupled to the second track 208 at asecond position 230 that is after the first portion 218 in the processdirection 216. In the present embodiment, the switch 210 is operable toselectively couple the first and second tracks 204, 208 at the secondposition 230, but other selective coupling mechanisms are alsocontemplated. The controller 214 is operatively connected to the switch210, and is further configured to operate the switch 210 to returnmaintenance platforms to the second track 208, and to enable mediaplatforms to remain on the first track 204.

As illustrated in FIG. 2, when the second track 208 is coupled with thefirst track 204, another continuous loop is formed by the second track208 and the first portion 218 of the first track 204. In the presentembodiment, the maintenance platforms 202 c-e move along the othercontinuous loop in a clockwise direction such that both the maintenanceplatforms 202 c-e and the media platforms 202 a and 202 b move along thefirst portion 218 in the same direction.

The receptacle 212 is positioned opposite the second track 208 and, forexample, between the second position 230 and the second track portion226. In other embodiments, the receptacle 212 is positioned elsewhere,such as between the second portion 226 and the first position 228. Afterperforming an operation on a printing station, a maintenance platformmay include extraneous matter that is desirably removed beforeperforming another operation. The receptacle 212 is advantageouslyoperable to remove matter from maintenance platforms.

The controller 214 is operationally connected to the receptacle 212, andis further configured to operate the receptacle 212 to remove materialfrom the maintenance platform 202 e positioned at the receptacle 212.Examples of such removal are described in further detail below. Oncematerial has been removed from a maintenance platform, such as theplatform 202 e, the controller 214 is further configured to operate theactuators of the second track 208 to return the maintenance platform tothe second track portion 226.

Maintaining the printing stations while minimizing interruptions in theprinting process of the system 200 can beneficially enable a steadyworkflow of printing operations, and a decrease in downtime for printingstation upkeep. It is also desirable that maintenance platforms notcollide with or impede the movement of media platforms. Advantageously,the controller 214 can be further configured to coordinate movement ofmaintenance platforms 202 c-e with the movement of media platforms 202 aand 202 b by selectively operating the actuators 215, 217 of the firstand second tracks 204, 208, and the switch 210. In other words, thecontroller 212 can be configured to schedule an operation on a printingstation during a period of time when a media platform is not occupyingin the printing station. For example, the controller 212 can scheduleoperations at predetermined intervals, after a predetermined number ofprinting operations, upon detection of a maintenance fault, such as aclog or contamination, or before or after a particular printingoperation.

Because the second track 208 is integrated with the first track 204 suchthat both maintenance platforms 202 c-e and media platforms 202 a and202 b pass through the first portion 218, a footprint of the printingsystem 200 is reduced relative to systems having a maintenance stationthat is separate from the printing stations. Further, the integratednature of the maintenance platforms 202 c-e with the workflow of theprinting process eliminates the need to connect and setup a maintenancestation, such as a maintenance cabinet, that may need to be individuallymoved to and configured to operate with each individual printingstation. The printing system 200 according to the disclosure enablesperforming different operations on different printing stations whileeliminating the often time consuming and complicated setup proceduresinvolved in conventional maintenance systems.

In an example of an operation on a printing station, when maintenanceplatform 202 c is positioned opposite the ejector head 216, thecontroller 214 is configured to operate the ejector head 206 to ejectmaterial onto the maintenance platform 202 c. Such ejection can purgeextraneous material or contaminants from the ejector head 206, remove orprevent a clog, clean material from the ejector head 206, or preventextraneous material from accumulating on, for example, the first track204.

FIG. 3 illustrates an exemplary embodiment of a maintenance platform 300that includes a plurality of wheels 302 configured to engage with atrack 304, such as the precision rails 38 (FIG. 11) and a tray 306configured to receive material ejected from an ejector head. The tray306 has a height 308 configured to retain material ejected therein. Inother embodiments, the platform 300 includes other movement mechanisms,such as slide surfaces configured to engage rails like the rails 22 inFIG. 11. In one embodiment, the platform further includes a magnetconfigured to engage with actuators in the track 304 to enable theplatform 300 to move along the track 304.

In one embodiment, the platform 300 comes to a stop beneath the ejectorhead to enable the ejector head to purge material into the tray 306.While integrating maintenance platforms with media platforms to performoperations as described above is beneficial to reducing delay in theprinting process, purging material from an ejector head may result in adelay before the ejector head is again usable for printing onto a mediaplatform. In another embodiment, the platform 300 remains in motionalong the track 304 while the ejector head purges material into the tray306 as the platform 300 passes by, thereby further reducing or eveneliminating the delay. The platform 300 can move along the track 304 atfull process speed, or at a reduced rate of speed in order to facilitatethe purging of material from the ejector head.

While a single operation may not fill the tray 306, removal of materialfrom the tray 306 can be beneficial so the platform 300 can becontinuously used. Advantageously, the receptacle 212 (FIG. 2) isoperable to remove material from maintenance platforms such as theplatform 300. FIG. 4 illustrates an exemplary embodiment of a receptacle400 that is operable to remove material 402 from the tray 306 of theplatform 300.

The receptacle 400 includes a vacuum source 404 configured to generate avacuum proximate to the tray 306 in order to remove material 402 fromthe tray 306. Advantageously, the vacuum source 404 further includes atube 406 configured to direct the vacuum generated by the vacuum source404. In one embodiment, the vacuum source 404 further includes anactuator (not shown) operatively connected to the tube 406 andconfigured to lower the tube 406 into the tray 306 for the removal ofmaterial 402 and raise the tube 406 out of the tray 306 to enable theplatform 300 to depart from the receptacle 400. In another embodiment,the actuator is configured to articulate the tube 406 in order to movethe vacuum source 404 within the tray 306 to remove material 402dispersed around various portions of the tray 306. The controller 214(FIG. 2) is operatively connected to the receptacle 400 and isconfigured to operate the vacuum source 404, the actuator connected tothe tube 406, and the actuators of the track 304 to remove the material402 from the tray 306 of the platform 300.

FIG. 5 illustrates another exemplary embodiment of a receptacle 500operable to remove material 502 from a maintenance platform 504. Thereceptacle 500 includes a heater element 506 and a heated umbilical 508,and the platform 504 includes wheels 302 configured to engage with androll along the track 304, a tray 306 configured to receive material 502,and a drain 510.

The heated umbilical 508 is configured to selectively couple with thedrain 510. In an embodiment, the receptacle 500 includes an actuator(not shown) operably connected to the heated umbilical 508 andconfigured to couple the heated umbilical 508 with the drain 510 whenthe platform 504 is positioned opposite the receptacle 500. The heaterelement 506 is positioned and configured to radiate heat into the tray306 to liquefy the material 502. The drain 510 is configured to enableliquefied material to exit from the tray 306 into the heated umbilical508. The heated umbilical 508 is heated, such as by, for example, aheating element, to enable the liquefied material to remain in aliquefied state while passing through the umbilical, which canbeneficially aid in the prevention of clogs or maintain a steady flow ofmaterial through the heated umbilical 508. In an embodiment, a furtheractuator is operatively connected to the heater element 506 and isconfigured to move the heater element towards the platform 300 to enablemore efficient radiation of heat to the material 502 and way from theplatform 300 to enable the platform 300 to depart from the receptacle500.

Other types and combinations of removal mechanisms are alsocontemplated, including but not limited to an articulated scoop operableto scoop material from within the tray 306, and a fluid source operableto introduce a fluid into the tray 306 in order to dilute, dissolve, orotherwise react with material in the tray 306 to facilitate removal ofthe material. In one embodiment, the receptacle 400 is configured tohouse a chemical reagent, and the tube 406 is further configured tointroduce the chemical reagent to material 402 in the platform 300 (FIG.4). As used herein, “reagent” or “chemical reagent” means a substancethat, when added to another substance, such as material in a tray,brings about a change in the other substance, and can include, forexample, liquidizers, solidifiers, solvents, and catalysts, and may ormay not be consumed when added to the other substance. Advantageously,the chemical reagent reacts with the material 402 but not the platform300. In one example, the chemical reagent is introduced in order totransform the material 402 into a liquefied form, whereby the liquefiedmaterial and the chemical reagent exit the tray 306 via a drain similarto the drain 510 (FIG. 5). In another example, a chemical reagent,light, or heat is introduced to material 402 that is in a liquid form inorder to solidify the material 402 before the material is removed fromthe platform 300. Some types of material ejected at a printing stationcan be volatile or dangerous, and it can be beneficial to cure,solidify, or otherwise modify the material before disposal. In anotherexample, the platform itself is disposed of.

Because a single operation may not result in the tray 306 beingcompletely filled with material, removing material from the platform 300less than every time the platform passes by the receptacle is beneficialso the tray can remain in use. In one embodiment, the controller 212 isconfigured to move the platform 300 to the receptacle 212 and operatethe receptacle 212 with reference to an estimated amount of materialejected into the tray during at least one operation, a predeterminednumber of operations, a predetermined time period or other criteria.

In one embodiment, the platform 300 further includes a sensor (notshown) configured to generate an electrical signal indicative of a fillcondition of the tray 306. In an example the sensor can be a weightsensor, or an optical sensor. The controller 214 (FIG. 2) can, forexample, be configured to move the platform 300 to the receptacle 212and operate the receptacle 212 with reference to the electrical signalgenerated by the sensor.

In another example of an operation, wiping a face of the ejector head isbeneficial to remove extraneous material or contaminants, remove orprevent clogs, and otherwise maintain the ejector head. FIG. 6illustrates an exemplary embodiment of a maintenance platform 600 thatis operable to wipe an ejector 602. The platform 600 includes wheels 302configured to engage with a track 304, and a wiper 604 connected to theplatform 600. In embodiments where the platform 600 further includes atray 306, the wiper 604 can be connected to the tray 306. The wiper 604is positioned and configured to wipe the ejector 602 when the platform600 is moved along the track 304 to the ejector 602. The wiper 604 canbe, for example, a rigid wiper that wipes as the platform 600 moves, awiper connected to a passive or active actuator, or another type ofwiping mechanism.

In a further example of an operation, covering an ejector head during aperiod of time in which the ejector head is unused can be beneficial toprotect the ejector head from damage and contamination, and to inhibitmaterial within the ejector head from solidifying and potentiallyforming clogs. In another example, some types of materials ejected by anejector head, such as UV curing material, can be volatile or dangerous,and covering the ejector head during periods of nonuse to limit theexposure of such materials to the environment can be beneficial.

FIG. 7 illustrates an exemplary embodiment of a platform 800 thatincludes wheels 302 configured to engage with and roll along the track304, covering members 802 a and 802 b, and an actuator 804. The coveringmembers 802 a and 802 b are configured to cover ejector heads 806 a and806 b. While the platform 800 is illustrated as including two coveringmembers 802 a and 802 b, the reader should understand that the platform800 can include different numbers of covering members to comport withdifferent numbers of ejector heads in an ejector head array.

The actuator 804 is operatively connected to the covering members 802 aand 802 b and is configured to cover the ejector heads 806 a and 806 bwith the covering members 802 a and 802 b when the platform 800 ispositioned opposite the ejector heads 806 a and 806 b. While FIG. 8illustrates the two covering members 802 a and 802 b as beingoperatively connected to a single actuator 804, other numbers ofcovering members can be connected to a single actuator. In oneembodiment, each covering member is operatively connected to arespective actuator to enable separate ejector heads to be individuallycovered or uncovered. The actuator 804 is, for example, operativelyconnected to the controller 212 (FIG. 2), which can be configured tooperate the actuator 804 to cover the ejector heads 806 a and 806 bduring a period of time in which the ejector heads 806 a and 806 b areunused, and can further be configured to uncover the ejector heads 806 aand 806 b to enable the platform 800 to depart from the ejector heads806 a and 806 b.

Other types of covering mechanisms are also contemplated such as, forexample, a covering mechanism configured to respond to a passiveactuator, a covering mechanism configured to selectively cover aparticular ejector head, and other types of covering mechanisms.

FIG. 8 illustrates another exemplary embodiment of a platform 900 usablein a three-dimensional object printing system. The platform 900 includesa surface 902 configured to receive material to form a three-dimensionalobject, and also includes a maintenance portion 904. As shown in FIG. 9,the maintenance portion 904 includes a tray 906 configured to receivematerial purged from an ejector head as described above in order toperform a maintenance operation, but the maintenance portion 904 canalso include other mechanisms in other embodiments, such as a wiper,covering member, and the like. The platform 900 is thus a hybridplatform that is both a media platform and a maintenance platform. In anembodiment, a printing system has one or more hybrid platforms inaddition to or instead of media platforms and maintenance platforms suchas the platforms 202 a-e in FIG. 2.

FIG. 9 illustrates an exemplary embodiment of a three-dimensional objectprinting system 1000 that does not include a second track 208 asdescribed above in FIG. 2 for the system 200. The system 1000 includeshybrid platforms 1002 a-d. Because each hybrid platform 1002 a-dincludes a contiguous area 1004 for object formation and a contiguousarea 1006 used for maintenance operations, the platforms 1002 a-d canremain on a unitary track 1008. Printing stations that include anejector head 1010 are positioned opposite a first portion 1012 of thetrack 1008, and a receptacle 1014 is positioned opposite the track 1008at a location spaced apart from the first portion 1012. In someembodiments, a switch 1016 is operable to selectively couple a holdingtrack 1018 to the track 1008 to enable at least one of the platforms1002 a-d to remain on the holding track 1018 during a period in whichthe one of the platforms 1002 a-d is unused.

Platforms used in the disclosed systems can include other maintenancemechanisms in addition to or instead of the tray, wiper, and coveringmembers described above. For example, a platform can include amaintenance mechanism, such as but not limited to, a blower operable toblow air over an ejector to remove contaminants, a vacuum sourceoperable to produce a vacuum proximate to an ejector head, or an emitterconfigured to emit a cleaning fluid onto an ejector head.

Those skilled in the art will recognize that numerous modifications canbe made to the specific implementations described above. Therefore, thefollowing claims are not to be limited to the specific embodimentsillustrated and described above. The claims, as originally presented andas they may be amended, encompass variations, alternatives,modifications, improvements, equivalents, and substantial equivalents ofthe embodiments and teachings disclosed herein, including those that arepresently unforeseen or unappreciated, and that, for example, may arisefrom applicants/patentees and others.

What is claimed is:
 1. A method for maintaining a three-dimensionalobject printing system comprising: operating a platform to move along asecond track past a first position where the second track is coupled toa first track, and along the first track in a process direction to aposition opposite an ejector head positioned opposite the first track;operating the platform to perform an operation on the ejector headpositioned opposite the first track; operating the platform to movealong the first track to a second position that is past the ejector headin the process direction; operating a switch to selectively couple thefirst track to the second track at the second position; and operatingthe platform to move past the second position to enable the platform toreturn to the second track.
 2. The method of claim 1 wherein operationof the platform occurs during a prescheduled maintenance time period. 3.The method of claim 1 further comprising: operating another platform tomove along the first track in the process direction past the ejectorhead; and operating the ejector head to eject material onto the otherplatform to form a three-dimensional object on the other platform,wherein the operation of the platform, the operation of the otherplatform, and the operation of the switch are selective to enableintegration of movement of the platform along the first track withmovement of the other platform along the first track.
 4. The method ofclaim 1 wherein the operation of the platform includes at least one of:(i) wiping the ejector head with a wiper positioned on the platform whenthe platform is positioned opposite the ejector head; (ii) operating anactuator operatively connected to a member to cover the ejector headwith the cover during a period in which the ejector head is unused; and(iii) operating the ejector head to eject material into a tray on theplatform.
 5. The method of claim 4 further comprising: removing materialfrom the tray on the platform into a receptacle positioned opposite aportion of the second track when the platform is positioned opposite thereceptacle.
 6. The method of claim 5, the removal of material from thetray includes at least one of: (i) operating a heat element that ispositioned in the receptacle to liquefy material within the tray toenable the liquefied material to exit the tray through a drain in thetray; and (ii) operating a vacuum source that is positioned in thereceptacle to produce a vacuum proximate to the tray to remove liquefiedmaterial from the tray.
 7. The method of claim 5, the removal ofmaterial from the tray includes either: (i) dispensing a liquefyingreagent into the tray to liquefy material in the tray; or (ii)dispensing a solidifying reagent into the tray to solidify material inthe tray.